The driver and two female passengers, aged 15 and 17, were seriously injured and rushed to Westmead Hospital.

But the third passenger, a 17-year-old girl, died at the scene of the crash.

The teenager driver remains under police guard, after undergoing mandatory drug and alcohol testing.

During a search of the vehicle, police found and seized drug paraphernalia, cash, and several white pills.

The impact of the collision was so severe it broke the electrical pole.

On Sunday afternoon, a 49-year-old woman died when her car left the road and hit a pole at Santuary Point on the state's south coast.

The crash was so severe it brought down power lines and trapped the driver, the sole occupant.

The woman was freed and treated by paramedics, but died before she could be taken to hospital.

Also on Sunday afternoon, a female pedestrian died in a carpark in North Ryde after she was hit by a car.

Police said initial reports indicate the woman fell before being struck by the car.

The driver, a 66-year-old woman, was not injured and was taken to Ryde Hospital for mandatory testing.

Police are urging any witnesses or anyone with dash cam vision to come forward.

Meanwhile another man died on Sunday morning after his trail bike crashed into a wire fence in Narromine.

The 18-year-old rider was found dead just before 7am.

On Saturday morning, a man died after his vehicle left the road and hit several trees near Balranald on the Victorian border.

The male driver, in his 30s, died, while his passenger was taken to hospital with minor injuries.